Communication networks are ubiquitous nowadays, and in particular, data networks (e.g., Internet) are becoming increasingly integrated in our day to day life. Maintaining the integrity of information flowing over networks is of critical importance for both privacy and national security reasons. Most existing networks, both commercial and military, have already integrated various data protection measures. At the heart of every existing security technology, the data protection relies highly on the public key/private key infrastructure (e.g., RSA) developed since 1970s for computer networks.
According to information theory, for the traditional key based encryption scheme, perfect secrecy is guaranteed only if a key size is at least as long as the source message. While providing a key size at least as long as a source message establishes provable security of the so-called one-time pad, such scheme is largely useless in the computer network era as key exchange is prohibitively complex.